Strange intermittent fault on 13 pin socket

[littlespark]

my caravan isn’t lighting up tail lights, but all other lights work fine.

However… while testing, I got a strange sequence of events.

I’ll also point out that the 13 pin socket has the left and right tail lights on different pins, so whatever it is, is affecting both sides.


Ok.. with vehicle engine running and headlights on, my trailer lights work. Unplug the trailer, plug it back in, lights still work… unplug trailer and plug caravan in, lights on caravan don’t work. Unplug caravan, plug trailer back in, trailer lights now don’t work.
Turn engine off, back on, and trailer lights come back on….

This can be repeated a number of times.


The trailer plug is a 13pin plug, but with only the 7 pins needed for lights. Caravan is full 13 pin


Either the relay in the vehicle is faulty, or could there be a relay box in the caravan?

Trailer is just plug, wires and lamps.

I’m going to buy a new 13pin plug for caravan and replace that, and maybe get a tester unit. Quite cheap on Amazon, so see how it goes.

 

[UNG]

How old is the tow vehicle and was the towbar and electrics a factory fitted option

Your fault may lie in a CANbus controller that controls the trailer / caravan road lighting and also controls the charging, permanent feed and fridge electrical supply in the caravan

To give you an idea of the towbar wiring methodolgy the last one I fitted for a family member the towbar wiring kit had 2 looms from the CANbus controller the controller was located on the offside rear wheel arch with one loom to the 13 pin socket and the other to the fusebox at the front this loom had 3 wires which were fitted into 3 fuse positions and fuses fitted for power in this loom there was also 6 CANbus wires 3 wires had to be removed from one of the CANbus plugs adjacent to the fusebox and 3 of the 6 wires where insert to replace the removed wires the other 3 wires in the loom had a pre terminated plug fitted and the 3 wires that were removed from the CANbus plug were inserted into a supplied socket and connected to the loom plug so the controller at the rear of the vehicle has a CANbus loop through, so effectively all the functions on the 13 pin socket are controlled by 3 CANbus wires and 3 +ve supplies the only other connection on the CANbus controller was a earth to a local earthing point on the body. After it's fitted all you need is the diagnostic tool to tell the vehicle it has a towbar

So without a diagnostic tool my first thought would be to check the earthing points for the towing electrics a 13 pin socket has 3 earths connected to it with different CSA's and obviously the 13 pin plug on the caravan has the same

 

[littlespark]

The tow vehicle is a 68 plate Rangerover evoque, and the tow bar was fitted after by a tow bar installer company, recommended by the dealership, and is the landrover electrics rather than some generic towing kit.
Only been fitted since May this year.

I’m going to email the company anyway explaining the fault and see if they have an idea.


Driving around today between jobs… I’m currently thinking a fault on the caravan, tripping something in the vehicle relay…. Stays tripped after unplugging the caravan. Restarting the engine resets it, allowing the trailer to work, but tripping again when caravan plugged in???

 

[UNG]

I would suggest the first place to look would be the 13 pin caravan plug, open it up and make sure there is no damp or corrosion in it that is often the source of most issues after that is the junction box usually on the inside of the chassis just beyond the caravan drawbar
If you have access to a vehicle diagnostic tool it may be worth reading the vehicle trouble codes to see if it has logged and retained any fault codes relating to the towing electrics

 

[brianmoooore]

Try powering up the caravan with a 12 volt PSU, directly to the appropriate pins in the 13 pin plug. This should give you an idea if there's anything wrong with the caravan, especially if you measure currents drawn.
Incandescent or LED lamps on the van?

 

[littlespark]

I forgot i started this thread, and had mentioned this issue on a different one... so ill update this from now on.

I haven't been in a rush to get this fixed, just because we weren't touring.... until now.

The caravan lights do work... It was serviced earlier in the year and they worked on their test rig... and i can get them to work by giving 12V to the correct pins on the plug.... Using a drill battery.

The car socket works... as it lights up the trailer no problem....

The difference is the trailer only has 2 lights each side, and they're LED.... The caravan has 4 or 5 filament types at 5W each when you add up all the amber markers, main tail lights, number plate light etc.

I still think its an 'overload' as the modern vehicle relay box cant handle up to 25W of load each side

Using the pin diagram in #2 as a guide, and if the same colours go right through the caravan.... could i break into the loom and use a couple of automotive relays.... Using pins 5 and 3 to switch the relays, and pin 9 to feed the contacts... switching onto the disconnected cables from pins 5 and 3 to the lights.... tapping into the earths where needed?

I suppose i could use just one relay, switched from only one pin.... but think the car would pick it up as a fault if they're not equal??
And i need to make sure the pin 9 feed can also take the load..... or take 12V for these lights from another source.... such as the drill battery.



or drive around in the daylight and not use the lights

 

[Avo Mk8]

Have you tried removing bulbs from the caravan each side to check it then works OK, to validate your theory it's excessive load? If that is the explanation, how about fitting led bulbs around the caravan instead of filament (if suitable available)?

 

[brianmoooore]

, how about fitting led bulbs around the caravan instead of filament (if suitable available)?

It's what I've done to mine, just to keep the currents and VD down.

 

[littlespark]

It’s in my thoughts, to change to LED.

Not that I can do that between now and Saturday.

 

[Mike Johnson]

The problem I have found with trailers and caravans is they are not used regularly enough and the bulb holders get corroded and cause high resistance in the unit, usually sorted by removing them, bit of emery paper on the contacts and some petroleum jelly to prevent occurrence. If that does not work then a good wiggle of the plug at the back of the car usually sorts it.

 

[brianmoooore]

Silicon grease. First saw it used/used it myself on single seat race cars.
The stuff I was dealing with generally used production car engines (Ford, Renault, etc), complete with their OE electrical looms, which were semi open to the weather, rather than being tucked away under a bonnet, so silicon grease was liberally applied to every plug and socket to ward off corrosion and water ingress.
Ever since, I've used it on every lamp, every sensor, every earth connection, and every plug and socket generally on all things vehicle related and rarely have a connection problem.

 

[Mike Johnson]

Comparison between Dielectric Grease and Petroleum Jelly/Vaseline:

Difference Between Dielectric Grease and Vaseline

Many a time, people ask questions on what they should use between dielectric grease and Vaseline for their motor vehicles, bikes, and motorcycles. Even though these two products are used mostly in the motor and

www.differencebetween.net

Short answer Dielectric Grease is a superior product, thanks for the heads up @brianmoooore every day is a school day.

Now to look up electrical contact cleaner to see if I have been wasting my time for all these years.

 

[Avo Mk8]

Now to look up electrical contact cleaner to see if I have been wasting my time for all these years.

It wasn't a waste of time if confronted with a badly behaved 405 line TV turret tuner, or a radio's noisy volume control or wave-change switch (at least as a 'quick fix'!)

 

[Mike Johnson]

It wasn't a waste of time if confronted with a badly behaved 405 line TV turret tuner, or a radio's noisy volume control or wave-change switch (at least as a 'quick fix'!)

Afraid I am old enough to have used all of those in the past, even a floor mounted tuner when ITV was first on offer, TV cabinet was full of valves so could not fit it inside.

 

[littlespark]

Here’s a thought.

The towing relay box that I think is tripping out because of relatively high load….
If I replace that with an older model of the same, will it cope with older filament bulbs?
I found the box that the whole kit came in, and it states LED COMPATIBLE in big bold font.

 

[Mike Johnson]

@littlespark Why a relay box in the caravan?

 

[littlespark]

@littlespark Why a relay box in the caravan?

From #1?

That was a question, and I know now there isnt a relay box in the caravan.... just the one in the car thats supplied with the wiring kit of the towbar.

 

[brianmoooore]

There should be a relay in the caravan connected to the 13 pin wiring, but it's nothing to do with the road lights.

 

[littlespark]

Yes... #1 was over a year ago now, and i did trace all the wiring when the van was emptied for its service. The road lights are direct from the plug.

So the problem... or issue by design, is in the tow car itself, not the caravan.

 

[nicebutdim]

Comparison between Dielectric Grease and Petroleum Jelly/Vaseline:

Difference Between Dielectric Grease and Vaseline

Many a time, people ask questions on what they should use between dielectric grease and Vaseline for their motor vehicles, bikes, and motorcycles. Even though these two products are used mostly in the motor and

www.differencebetween.net

Short answer Dielectric Grease is a superior product, thanks for the heads up @brianmoooore every day is a school day.

Now to look up electrical contact cleaner to see if I have been wasting my time for all these years.

I use both on battery chargers for Li-ion cells. Contact cleaner for its intended purpose every once in a while and dielectric grease to keep cleaning requirements to a minimum, thus ensuring accurate charging and prolonged cell life.